His point was that the Real IRA is a similar “loose affiliation” — that it also has a number of parts, and different leaders doing different things. That makes it difficult for the dissidents to achieve “an organisational thrust” but it presents the intelligence world with problems.

“We have to have a handle on all of them,” the security source said.

But there was no “handle” on those behind the shootings at Massereene Barracks, and then — just 48 hours later — the Continuity IRA attack in Craigavon.

“They are trying to become a more unitary organisation — more cohesive,” the security source said of CIRA, and both that group and RIRA have “put effort” into obtaining weapons.

The big police effort now is on identifying those who used the guns and carried out the three killings in recent days.

In all of 2008 there were 15 dissident attacks — four of them involving incendiary devices and 11 shooting and bombing incidents directed against the security forces, mainly police.

In the circuitry, detonation and booster methods and explosive mix in their devices, the dissidents have made some improvement.

This is something that was seen in a recent security operation in Castlewellan, when it took five days to dismantle an abandoned bomb.

It is thought to have been destined for the Ballykinler Army base, but the security forces did not know it was coming. “I wouldn’t count that as one we interrupted,” a source told this newspaper — and that is another indication of gaps in the intelligence picture.

There have been reports that the bomb was fitted with a sophisticated anti-handling device but it turned out not to be the case.

After the murders of the last week or so, the investigating teams are looking for evidence, and MI5 and the PSNI intelligence branch C3 are painstakingly trying to piece a jigsaw together.

Their hope is that they can get to the dissidents before they get to their next target.